Java – why is my field not initialized to the value I gave it

I have the following courses:

public abstract class AClass {

    public AClass() {
        aMethod();
    }

    abstract protected void aMethod();

}

public class SubClass extends AClass {

    private int x = 5;
    private static final int y = 6;

    @Override
    protected void aMethod() {
        System.out.println("x: " + x + " | y: " + y);
    }

}

public class Main {

    public static void main(String[] args) {
        new SubClass();
    }

}

Running main prints the following: X: 0 | Y: 6

Why does 0 print x?

Solution

The cause of the bad behavior is the wrong initialization sequence:

>New subclass() executes aclass constructor > aclass constructor calls amethod() > amethod() shows x (0 so far), y is 6 because it is static) > subclass initializes its non static field, so x becomes 5

To avoid confound, do not call virtual methods (especially overriden) in constructors.